Monophyletic origin of domestic bactrian camel (Camelus bactrianus) and its evolutionary relationship with the extant wild camel (Camelus bactrianus ferus)

R Ji,H Gao,J Yu,P Cui,J Geng,H Meng,F Ding,H Zhang,S Hu

doi:10.1111/j.1365-2052.2008.01848.x

Abstract

The evolutionary relationship between the domestic bactrian camel and the extant wild two-humped camel and the factual origin of the domestic bactrian camel remain elusive. We determined the sequence of mitochondrial cytb gene from 21 camel samples, including 18 domestic camels (three Camelus bactrianus xinjiang, three Camelus bactrianus sunite, three Camelus bactrianus alashan, three Camelus bactrianus red, three Camelus bactrianus brown and three Camelus bactrianus normal) and three wild camels (Camelus bactrianus ferus). Our phylogenetic analyses revealed that the extant wild two-humped camel may not share a common ancestor with the domestic bactrian camel and they are not the same subspecies at least in their maternal origins. Molecular clock analysis based on complete mitochondrial genome sequences indicated that the sub-speciation of the two lineages had begun in the early Pleistocene, about 0.7 million years ago. According to the archaeological dating of the earliest known two-humped camel domestication (5000–6000 years ago), we could conclude that the extant wild camel is a separate lineage but not the direct progenitor of the domestic bactrian camel. Further phylogenetic analysis suggested that the bactrian camel appeared monophyletic in evolutionary origin and that the domestic bactrian camel could originate from a single wild population. The data presented here show how conservation strategies should be implemented to protect the critically endangered wild camel, as it is the last extant form of the wild tribe Camelina.

Highlights

The PCR primers (Table S2) used for the initial amplification were designed based on the mitochondrial genome sequence of wild camel (C. bactrianus ferus) from public databases
We first examined the intersubspecific variations that are important in understanding the evolutionary history of the bactrian camel
To further investigate the evolutionary relationship between the extant wild camels and domestic bactrian camels, we sequenced five mitochondrial genomes from two wild and three domestic individuals, using 23 pairs of universal PCR primers for the initial amplification based on the mitochondrial sequence of C. bactrianus ferus from the public databases (Table S2 and Fig. S2)

Summary

Introduction

Daniel Potts once said that if the Silk Road may be described as the bridge between the Eastern and Western cultures, the bactrian camel should rightfully be considered as the principal means of locomotion across that bridge (Potts 2005). Previous modern archaeological evidence suggests that the original habitat of the wild bactrian camel extended from the great bend of the Yellow River in north-western China through Mongolia to central Kazakhstan (Bannikov 1976; Schaller 1998; Nowak 1999), and it may have been domesticated in different regions of the East (multiple origins) about 5000 years ago, after which it subsequently spread westward towards Central Asia (Han et al 2002).

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Discussion

Conclusion